Underground or buried parking lots, as well as other structures of this type, undergo deformations that can occur due to fluctuations in the temperature of the outside air, as well as during uneven soil precipitation. Deformations are also obtained during seismic as well as other phenomena. Under the influence of the above factors, self-stresses can occur, which cause cracks in the structures. They reduce the bearing capacity and lead to the fact that the waterproofing layer loses its integrity.
In order to exclude and prevent this phenomenon, there should be expansion joints in the enclosing and supporting structures of underground structures. They reduce bending loads at the points of greatest deformation, in addition, such phenomena due to the seams are not dangerous.
Solution
Waterproofing of the expansion joint should be carried out after choosing the technology of work. Due to the fact that the loads on such structures are very high, as for the transverse and longitudinal directions, expansion joints in underground structures should differ from those available in other parts of the structures. Quite often, it is necessary to use an integrated approach, which provides for several systems, as a result of which the waterproofing layer shows the qualities of reliability and durability. Today, several methods are known for arranging such joints, which depend on the width of the joint, deformations and the technology of waterproofing structures. Before choosing a solution, you need to familiarize yourself with all possible options, considering their pros and cons.
The use of sealants
Waterproofing of the expansion joint can be carried out using sealants that are used after the completion of monolithic work. This option involves filling the joint with a two-component composition, which has the qualities of high adhesion to concrete. As a substrate, a sealant is used to secure the sealant layer, its width should correspond to the size of the seam.
Units for waterproofing expansion joints can be easily secured by this method, which is the simplest, but has some limitations on the performance of work. They are expressed in a small joint width, which does not exceed 30 mm, while its deformability should not be more than 15%. Among other things, structures constructed in this way should not experience constant groundwater pressure.
In order to waterproof such a deformation seam that will be used under the influence of groundwater pressure, in addition to this method, a protective casing compensator, which is made of a 0.5 mm stainless steel sheet, should be used.
Using a flexible membrane
When waterproofing the expansion joint is necessary, you can increase its width, and then use a flexible membrane. As her can act "Lastina C". Its installation is carried out by fixing using metal clamping strips on the edges of concrete. The surface is pre-treated with a sealant that has high adhesion.
The disadvantage of this method is that it cannot be used in structures that are constantly exposed to groundwater pressure. If such conditions are met, then in addition to the membrane, you can use a protective casing compensator, which is made of stainless steel. Penetrating materials can be used as the primary waterproofing for the two aforementioned systems. They are applied to the surface of the concrete and make it waterproof. The disadvantage of such a waterproofing is that in the event of cracking, the structure may lose the integrity of the waterproofing, which causes water to enter the structure.
Application of embedded elements
Waterproofing of the expansion joint can be carried out using embedded elements, which have the form of profiles made of PVC or rubber. At the same time, a waterproofing key is laid, which is done at the time of the execution of monolithic concrete work. During such manipulations, special inserts must be mounted in the formwork, using them, after pouring concrete, it will be possible to form a deformation seam, concreted with a waterstop, it will be inside the ceiling or wall.
Waterstops are made of different materials, such as PVC or rubber. They have different shapes and installation methods in a monolithic design. When waterproofing expansion joints by this method, it should be borne in mind that the performance in different types of dowels in the directions of tension, compression, longitudinal and transverse shear, as well as water pressure can be different. Everything will depend on the expected deformation, which will determine the type of key. In addition to waterproofing, special concrete grades are used that have waterproof properties. As an alternative solution, waterproofing, which is based on membranes for underground structures, can be used.
Using surfaced material
Waterproofing of expansion joints from the inside can be carried out using a polymer bitumen material, which is laid according to the method of deposition. Among other things, a sealing harness is used. This system is mounted after the completion of monolithic concrete work. The deposited material, which does not have a base, has a transverse and longitudinal elongation at break equal to 1000%. This indicates that waterproofing can stretch 10 times.
For the reason that the material is delivered in rolls with a width ranging from 330 to 1000 mm, it can be used for all types of expansion joints. These can be seams at the joints of vertical and horizontal plates, in the area of fillet joints and joints of complex configuration. The deposited material is installed using a gas burner. When such waterproofing of expansion joints in underground structures is used, resizing can reach 50 mm without restrictions. If this value is exceeded, then a complex should be used that provides for the use of injection systems.
The use of waterproofing "Neodyl"
The waterproofing of expansion joints using the Neodyl system provides for the deposition of material on the coating lining. Next, sealing with a tourniquet and protection of the deposited upper layer of the coating. When laying, it is necessary to take into account the heat resistance of bitumen, which is 100 ° C. The system comes into action if the main waterproofing of the seam is damaged.
A special sealant must be supplied to the seam through pre-installed pipes under pressure, which penetrates the seam cavity and makes it completely airtight. For the system, the Tegapar 431 TP polymer-bitumen membrane is used as the main waterproofing, which is resistant to aggressive environments, is easy to install, and has large dimensions.
Features of using waterstops
Waterproofing of expansion joints in underground structures, the nodes of which can consist of a special key, has the form of a tape installed in the formwork at the stage when the monolith must be filled in parts. This allows you to get moving expansion joints. There are several special cavities and beads in the waterstop, with the help of which the element is easy to install and guarantees reliability, as well as ductility of joints.
Polyurethane Sealant Technology
Waterproofing of expansion joints from the inside, as mentioned above, can be carried out using polyurethane sealant. To do this, they should be cleaned of old waterproofing, dust and delamination of concrete, lay a tourniquet of foamed polyethylene. It is required to reduce the consumption of sealant. The inner surface is treated with a primer to increase adhesion. Using a spatula or a gun, the sealant is placed in the cavity of the expansion joint.
Conclusion
In order for the waterproofing joints of the expansion joints to be as reliable as possible, when filling them with sealant, the surface must be smoothed with a spatula using soapy water until you can get an even base. It is important to remember that the laid harness should be 10 mm wider than the seam width.